Post on 25-May-2019
Changes of organic matter in soils irrigated with reclaimed wastewater
Bernd Marschner, Elisabeth JüschkeRuhr-University Bochum
Yona Chen, Jorge TarchitzkyHebrew University Jerusalem (Rehovot)
within the GLOWA Research Framework (BMBF & MOST)
Background
! In many countries, water demand is expected to increase due topopulation growth and improved standard of living.
! Freshwater resources are limited, often overexploited or deteriorateddue to pollution.
! Global climatic change may aggravate this situation by reducing precipitation and increasing evapotranspiration.
! "Clean" freshwater from ground- and surface waters will be preferentially allocated for use as drinking water and for certain industrial processes.
! For agricultural production, irrigation will therefore increasingly have torely on marginal waters, such as saline waters or treated wastewater.
0
500
1000
1500
2000
renewable watersources
mio
m3
Other Aquifers and surface watersSea of GalileeMountain AquiferCoastal Aquifer
Water sources and water use in Israel
1600
0
500
1000
1500
2000
renewable watersources
mio
m3
Other Aquifers and surface watersSea of GalileeMountain AquiferCoastal Aquifer
0
500
1000
1500
2000
water use
mio
m3
industry
municipal & household
agriculture
1200
600
Water sources and water use in Israel
1600deficit > 400
> 2000agricultural sources
fresh water75%
treated wastewater
20%
brackish water
5%
additional sources (350 - 400 mio m3/yr)
fossile water19%
desalini-sation
5% treated wastewater
76%
Problems associated with the use ofreclaimed wastewater for irrigation
! Microbial pathogens (i.e. coliformes) may contaminate food crops.
! High nutrient loads (esp. N, P) increase the risk of groundwater eutrophication.
! Elevated salt loads can cause soil degradation and groundwatersalinisation.
! Elevated inputs of heavy metals, organic pollutants, hormones and antibiotics may enter food chain or groundwater resources.
! Inputs of particulate and dissolved organic matter can affect mobility of contaminants and physical, chemical or biological soil properties.
Treated wastewater as irrigation water source (Ramat Hakovesh)
* present regulation for BOD in Israel 20 mg/Lproposed new regulation 10 mg/L
parameter unit effluent freshwaterEC dS/m 2.3 1.0Cl mg/L 364.0 201.0Na meq/L 21.4 4.3
Ca + Mg meq/L 6.1 4.1pH 8.3 7.4
DOC (Dissolved Organic Carbon) mg/L 23.5 1.1 BOD (Biological Oxygen Demand) mg/L 59.9 *COD (Chemical Oxygen Demand) mg/L 234.0
~ 1~ 1
1. Site screening (DOM quantity and quality)
2. Repeated sampling (DOM seasonality)
3. Laboratory experiments- soil respiration- substrate induced respiration (Priming)- microbial biomass (CFE)- microbial activities (FISH)
4. Soil organic matter inventories
Methodological approach
Basra
Ramat Hakovesh
Yagur
Gaaton
Sampling sites for screening
Arad
Percolation of soil samples
peristaltic pump
vacuum pump
- 65 hPa
glass filter plate(pores < 16 µm)
250 ml 1 mM CaCl2
irrigation: 25 mm h
duration: 6 h
-1
Soil80 cm3
membrane filtration0.45 µm
Texture, Corg, Nt, Cmic, δ13C
pH, EC, anions, DOC, UV-absorbance, fluorescence,biodegradability, XAD8-fractionation, KDOC, δ13C
MultiplexerKonduktometer
Computer
Respicond
0000,00 mS
1 96
Incubation of soil samples(CO2, 14CO2, 13CO2)
Extractable DOC in the soils from the different study sites
0
10
20
30
40
50
60
RamatHakovesh-
field
RamatHakovesh-orchard 10
cm
RamatHakovesh-orchard 20
cm
Basra Yagur Gaaton
DO
C c
onte
nt [m
g kg
-1]
freshwater irrigated soil
effluent irrigated soil
Humification Index (HIX) of extractable DOC in the soils from the different study sites
0.0
0.2
0.4
0.6
0.8
1.0
RH I RH II 10 cm RH II 20 cm Yagur Basra Gaaton
HIX
freshwater wastewater
0
10
20
30
40
50
60
wastewaterirrigated
freshwaterirrigated
wastewaterirrigated
freshwaterirrigated
DO
C [m
g kg
-1]
hydrophilic DOChydrophobic DOC
December June
Seasonal differences in DOC properties(Ramat Hakovesh field)
" Consistently more DOC in wastewater irrigated soils" Preferential release or production of hydrophilic DOC compounds
during rainy season in both sites
Biodegradability and specific UV absorbance(Ramat Hakovesh field)
0
10
20
30
40
50
60
1.5 2.0 2.5 3.0 3.5 4.0
specific UV254 absorbance [l m-1 mg-1]
biod
egra
dabi
lity
[%]
fw December
ww Decemberfw June
ww June
" Easily degradable DOC compounds with lower SUVA are released during rainy season (Dec – May)
" Wastewater irrigation effects of previous year are more pronounced after rainy season (due to higher microbial activity?)
1. 4-month incubation of soil samples from two sites with fresh- and wastewater irrigated field plots, irrigated daily with fresh- or wastewater (factorial design).- monitoring of CO2-evolution- microbial biomass- microbial cell counts (fluorescence in-situ hybridisation)
2. 4-week incubation of soil samples with substrate additions for thedetermination of priming effects(glucose, 14C-fructose, 14C-alanine)- CO2, 14CO2
Soil incubation studies
Soil respiration
Hamra soil
0
2
4
6
8
10
12
14
16
18
freshwater soil wastewater soil
accu
mul
ated
CO
2 in
mg
g-1
Vertisol
0
2
4
6
8
10
12
14
16
18
freshwater soil wastewater soil
accu
mul
ated
CO
2 in
mg
g-1
fw irrigationww irrigation
CO2 evolution accumulated in a 4 month irrigation experiment
"microbial respiratory activity is higher in soils originating from wastewater irrigated sites
"Wastewater irrigation in the lab stimulates microbial activity in all soils
0.0E+00
2.0E+08
4.0E+08
6.0E+08
8.0E+08
1.0E+09
fw-fw fw-ww ww-fw ww-ww fw-fw fw-ww ww-fw ww-ww
Hamra Vertisol
bact
eria
per
mL
soil
solu
tion
(equ
ival
ent t
o 0.
4 g
dry
mat
ter)
DAPIEUB338
38 %
51 %
50 % 50 %
44 %
52 %
41 %
51 %
Bacterial counts after 4 months of irrigation
0
100
200
300
400
500
control w/ fructose w/ alanine
CO
2-C
[µg
g-1]
feshwater wastewater
Effects of substrate additions on soil respiration (Ramat Hakovesh orchard, 10-20 cm)
" Elevated CO2-release from wastewater irrigated soil can not be attributed to higher Corg content
" Microbial activity in the freshwater irrigated soil is limited by theavailability of easily degradable substrates
+36%
+69%+7%+16%
0
5
10
15
20
25
30
control w/ alanine w/ fructose
CO
2 [%
of S
OC
]freshwater irrigated plotwastewater irrigated plot
+170%
+238%
+157%+186%
Priming effects after substrate additionsHaMapil (90-100 cm)
" Microbial activity in the subsoil is highly C-substrate limited" Microbial activity is higher under effluent irrigation, but more
stimulated by substrates under freshwater irrigation
0-10 cm
0.0
0.5
1.0
1.5
2.0
2.5
0 1 2 3 4time (d)
CO
2 (m
g h-1
)
freshwaterwastewater
20-30 cm
0.0
0.5
1.0
1.5
2.0
2.5
0 1 2 3 4time (d)
CO
2 (m
g h-1
)
freshwaterwastewater
90-100 cm
0.0
0.2
0.4
0.6
0.8
1.0
0 1 2 3 4time (d)
CO
2 (m
g h-1
)
freshwaterwastewater
Soil respiration after glucose addition (SIR)HaMapil
" Stimulation of microbial respiration by glucose is more rapid and stronger in the wastewater than in the freshwater irrigated soil.
-200
-150
-100
-50
00.0 0.5 1.0 1.5 2.0
SOM (%)
soil
dept
h (c
m)
freshwaterwastewater
Yagur (35 yrs)
-200
-150
-100
-50
00.0 0.5 1.0 1.5 2.0
SOM (%)
soil
dept
h (c
m)
freshwaterwastewater
Misra (12 yrs)
-150
-100
-50
00.0 0.5 1.0 1.5
SOM (%)
soil
dept
h (c
m)
freshwaterwastewater
Basra (30 yrs)
-150
-100
-50
00.0 0.5 1.0
SOM (%)so
il de
pth
(cm
)
freshwaterwastewater
Arad (10 yrs)
+8 t/ha
-15 t/ha
-12 t/ha
-40 t/ha
Soil organic matter inventories
Summary and conclusions
! Wastewater irrigation has no consistent effects on the quantity or quality of DOC (or SOC) in topsoils.
! Microbial activity and SOM mineralization are stimulated by the application of wastewater.
! Microorganisms in wastewater irrigated soils are more adapted to the rapid mineralization of easily degradable substrates, but priming effects are more pronounced in soils from freshwater irrigated sites.
! In subsoils, wastewater irrigation can stimulate microbial activity to such an extent, that SOM is mineralized at a higher rate than it is replenished from organic inputs with wastewater.
! This is attributed to the inputs of easily degradable dissolved organic compounds with the wastewater.
! Possibly, leaching of degradation products of particulate wastewater-borneOM also contribute to such priming effects.
! A depletion of soil OM pools at a rate of >1 t ha-1 annually may have long-term effects on soil fertility and is a source of CO2 to the atmosphere.
Thank you
Dankeschön
Relevance of the results for the planned research activities
Priming effects seem to be ubiquous in soils that receive regular inputsof easily degradable organic compounds (such as manures). With our experimental approach, this can be detected at an early stage and thus may help to prevent long-term detrimental changes in soil properties.
Soluble organic compounds have important ecological functions such as substrates for microbial activity or carriers for pollutants.
DOC amounts and properties are easily determined and together with data on soil microbial activity are sensitive parameters and powerful tools for the detection of soil quality changes.
Both soil types are effected differently by effluent irrigation
Bacterial activity is increased through effluent irrigation
Hamra: increase of activity with irrigation duration in effluent irrigated soil
Vertisol: irrigation duration has no obvious effect on the activity of bacteria in effluent irrigated soil
The strongest increase in activity could be determined in effluent irrigated soil under effluent irrigation
Microorganisms are already adapted to the compounds of the effluent water as substrate and develop better after irrigation break during winter
...
Conclusion
direct and indirect methods for determination of activity of the soil bacteria correlateand a shift to an increase of activity can be seen
effluent irrigated soil in the field experiment appeared to have clearly higher activity and the activity declined with depth
freshwater irrigated soil showed no higher bacterial activity and no effects in depth
Treated wastewater used as irrigation water causes a lasting change of bacterial activity in soils. This depends
on the soil type as well as on the irrigation duration.
...
Conclusion
... stimulation or inhibition of transformation and utilisation of SOM after addition of organic substrates
Priming-Effects are ...
Kontrolle ohneSubstrat
Substrat A Substrat B
positiv
negativ
12CO2frei
gese
tzte
s C
O2
12CO2
12CO2
14CO2
14CO2
zusätzliches12CO2
Kontrolle ohneSubstrat
Kontrolle ohneSubstrat
Substrat A Substrat B
positiv
negativ
12CO2frei
gese
tzte
s C
O2
12CO2
12CO2
14CO2
14CO2
zusätzliches12CO2
positive
control without
substrate
substrate A
substrate B
rele
ase
of C
O2
additional 12CO2
negative
0.6 M KOHMultiplexerKonduktometer
Computer
Respicond
0000,00 mS
1 96
12CO214CO2
measurement of CO2 release
addition of 14C-fructose or 14C-alanine
To slide 5 (priming effects)
" Priming effects in freshwater irrigated soil correlate with increased Cmic
" Lack of priming effects in ww soil despite similar substrate utilization indicates that substrates are not limiting microbial activity
Effects of substrate additions on the mineralization of SOM (Ramat Hakovesh orchard, 10-20 cm)
cont
rol
cont
rol
+36%
+69%
0
2
4
6
8
freshwater irrigated soil wastewater irrigated soil
Cor
g min
eral
isat
ion
[%]
w/ f
ruct
ose
w/ f
ruct
ose
w/ a
lani
ne
w/ a
lani
ne
Results
CO2 evolution per mg microbial biomass Ccylinder experiment
0.00
0.01
0.02
0.03
0.04
0.05
0.06
before experiment after experiment under fw irrigation
after experiment under ww irrigation
CO
2in
mg
h- 1m
g C
mic
-1
Hamra - freshwater irrigated soilHamra - effluent irrigated soilVertisol - freshwater irrigated soilVertisol - effluent irrigated soil
Field experiment HaMa´pil
Total and metabolic active bacteria
1.0E+05
5.1E+06
1.0E+07
1.5E+07
2.0E+07
2.5E+07
0-10 cm 10-20 cm 20-30 cm 1 m
bact
eria
per
mL
soil
solu
tion
(equ
ival
ent t
o 0.
4 g
dry
mat
ter)
DAPI-fwEUB338-fwDAPI-wwEUB338-ww
0.100.921.172.03effluent irrigated soil
0.150.300.492.23freshwater irrigated soil
1 m 20-30 cm10-20 cm0-10 cmTab.: Corg in %
21 %
27 %19 %
34 %
83 %
52 %
26 %
9 %
freshwater irrigated soileffluent irrigated soil
Increase of active bacterial cells in % during 4 months of effluent irrigation
-2
42
-28
-11
8
2214
46
-40-30-20-10
0102030405060
after 5 weeks after 10 weeks after 14 weeks after 18 weeks
%
Hamra
Vertisol19 20 20
46
1518
-31
17
-40-30-20-10
0102030405060
after 5 weeks after 10 weeks after 14 weeks after 18 weeks
%
R²=0.96
Land use: Effects of effluent irrigationLand use: Effects of effluent irrigation
Summary
• Irrigation with treated wastewater influences the amount and properties of organic soil components
• OM level increases in the topsoil of effluent irrigated soils, yet it is depleted from deeper horizons
• Shifts in DOC quality during seasons were observed
Increased indication of priming effects
leads to higher mineralisation of SOM, also in deeper horizons
additional DOC as nutrient source in the effluent irrigated soil
Mineralisation of soil organic carbon [%]Ramat Hakovesh orchard 10-20 cm
(incubation 31 days)
+36%+16%
+69%+7%
0.0
2.0
4.0
6.0
8.0
freshwater irrigated soil effluent irrigated soil
Min
eral
isat
ion
of S
OC
[%]
controlfructose
alanine
• in effluent irrigated soilhigher mineralisationin the control
• addition of substrates results in positive priming effects
• stronger effects infreshwater irrigated soils
effluent water contains fresh organic substrates, which enhance themineralisation of SOM already in the field
in these soils priming may occur directly after addition of effluent water,easy available pool in the soil is used all the time
Priming Effects